1. Field of the Invention
This invention relates generally to an LED headlamp assembly for a vehicle and, more particularly, to an LED headlamp assembly for a vehicle that includes a plurality of LED units mounted to a common carrier and a mounting frame that is positioned behind the carrier for mounting the headlamp to the vehicle, where the mounting frame supports actuators and pivots that position and direct the carrier in such a manner that the mounting frame, actuators and pivots do not interfere with the heat sinking of the LED units.
2. Discussion of the Related Art
Vehicle styling and appearance provides significant and important advantages for attracting customers. One recognized area that is known to enhance vehicle attraction is the appearance and design of the various vehicle lights, sometimes referred to as the vehicle's jewels, including, but not limited to, headlights, tail lights, turn signals, back-up lights, center high mounted stop lamps (CHMSLs), running lights, fog lamps, side markers, etc. In fact, modern vehicle designs pay close attention to the styling and design of the vehicle lights.
Current vehicle lights employ various types of light sources suitable for different designs and conditions. For example, vehicle lighting designs have employed incandescent lamps, neon tubes, halogen lamps, xenon lamps, etc. Some modern vehicle light designs have employed light emitting diodes (LEDs) that are able to provide various colors in an inexpensive and compact arrangement. LEDs typically do not suffer from burnout, and have good drive characteristics, high luminance, high efficiency, high vibration resistance and durability. to endure repetitive on/off operations. Therefore, LEDs have been attractive for vehicle lighting.
LEDs emit monochromatic light at wavelengths depending on the doping characteristics of the LED semiconductor material. Traditionally, the most efficient LEDs have emitted red light, green light or blue light. It has heretofore not been possible to provide an LED semiconductor material that emits white light. However, various LED designs are available that convert colored light to white light. One design employs a combination of red, green and blue LEDs arranged close together. The light from the LEDs is combined and diffused to provide the white light. However, these types of LED designs have typically been limited because of variances in tone, luminance and drive power of the different LEDs.
Another white light LED design employs a colored light LED and a fluorescent material that absorbs the colored light and emits white light. U.S. Pat. No. 6,069,440, issued May 30, 2000 to Shimizu et al., discloses a white light LED including a layer of phosphor deposited over a blue light LED. The phosphor includes a fluorescent that absorbs the blue light and emits white light. In one particular design, the LED material is InGaN and the phosphor layer includes an yttrium-aluminum-garnet fluorescent material.
There is a push in the automotive industry to develop white light LEDs so that LEDs can be used in vehicle headlamps. Important design concerns for vehicle headlamps come into play when using the existing technology for generating white light from LED semiconductors, such as employing blue LEDs in combination with a phosphor layer. Particularly, intensity and directional considerations are important for the tightly regulated headlamp requirements. Further, providing a compact, efficient, low cost and aesthetically pleasing LED package is necessary.
Known LED headlamps typically include a plurality of LED units, each including one or more LEDs, mounted to a common carrier. The LED units generate considerable heat. This heat needs to be sinked away or removed from the unit so that the life and performance of the LED unit is not significantly degraded. To provide the heat sinking, the back of the carrier sometimes includes a suitable heat sink, such as spaced apart fins or pins, that draws heat away from the carrier generated by the LED units. Other, non-passive heat sinking techniques are also know to draw heat away from LED units of this type.
Further, the LED units need to be sealed from the environment so that moisture does not come in contact with the LED units and affect their operation. Also, it is necessary that actuators and pivots be provided to position the headlamp to satisfy its beam directional requirements. It has been suggested in the art that a flexible bellows could be coupled to the carrier and a headlamp housing so that the entire carrier including the LED units can be moved relative to the housing by actuators and pivots for directional purposes without affecting the compartment seal integrity. These designs typically require that the actuators and pivots be mounted to the edge of the carrier so as to not interfere with the heat removal capability of the heat sink.
The opening that vehicle manufacturers allow for headlamps is usually limited and tightly controlled. It is sometimes necessary to use as many LED units in an LED headlamp as possible to provide the required beam intensity. Because the actuators and pivots that adjust the position of the carrier are positioned at the edges of the carrier, this space is generally not available to be used for LED units, thus limiting the intensity for a particular sized headlamp opening. It would be desirable to move the actuators and pivots to a different location so that the entire opening is available to be filled with LED units.